Page 2 Science Study Guide for the HiSET® Test

Physical Science

The physical sciences study the makeup, interactions, and behaviors of matter. The main disciplines are physics and chemistry.

Properties

The properties of a substance are observable characteristics that can be measured. Some properties or combinations of properties are specific to a given substance and can be used to identify it. Other properties, such as temperature, are a result of external actions on a substance.

Position, Motion, Mechanical Energy

The study of moving objects provides an introduction to concepts that are encountered in many other areas of physics.

Laws of motion.

Newton formulated three laws of motion that form the basis of understanding how forces affect objects and cause them to move or change their motion. They can be summarized as follows:

Objects persist in their state of rest or constant motion unless and until acted on by an external force.
Force = mass x acceleration.
For every action there is an equal and opposite reaction.

Gravity

Newton also established a law of gravitation that still forms the basis of spacecraft navigation today. He established that the force of gravity is proportional to the mass of the objects and inversely proportional to the square of their distance.

Other Forms of Energy

The other areas of study in physics draw heavily on the concepts introduced in the study of mechanical energy, especially unites of measurement, forces, and laws of conservation.

Light and Sound

Experiments have shown that light exhibits the characteristics of particles and waves. However, the wave properties of light are most important in understanding light. The speed of light is a fundamental physical constant represented by c. Wavelength x frequency = velocity. Sound is also a wave phenomenon.

Magnetic forces are related to electricity. Electric currents generate a magnetic field that can move a compass needle. Magnets can exert force on current-carrying wires, and the motion of wired through a magnetic field will induce an electric current in the wire.

Matter

Matter is composed of simple particles called atoms. The study of the particle nature of matter is important in understanding how matter changes with temperature and which substances will react with each other.

Matter Basics

Atoms are the smallest particle of a pure substance. Atoms of different substances combine to form molecules. The behavior of substances—such as change of state from solid to liquid to gas—is understood as the motion of these particles at extremely small size scales.

Atoms have a nucleus consisting of uncharged neutrons and positively charged protons. The nucleus is surrounded by electrons. Neutrons and proton are thousands of times more massive than electrons, yet the nucleus occupies a tiny fraction of the space of an atom.

Chemical Reactions

Atoms form bonds and enter into chemical reactions based primarily on their electron configurations. Understanding of chemical reactions will come in large part from learning these configurations and how they change during a reaction.

Chemical bonds

Chemical bonding is driven primarily by the tendency of atoms to gain stable outer electron shells, usually with eight electrons. This tendency will determine whether a given atom will react with another and how many of each atom will be in the resulting molecule.

The important principle in chemical reactions is the conservation of matter. All chemical reactions must be balanced, showing the same number of each kind of atom entering and leaving the reaction. The mole, or gram molecular weight, is the unit used when calculating quantities in reactions, known as stoichiometry.

Acids and bases can be defined by the ions they produce in solution. Acids produce H+ ions and bases produce OH- ions. However, they can also be defined by whether they donate protons (acids) or accept protons (bases). Both definitions are useful in understanding different aspects of acid-base chemistry.

The behavior of gasses follows from the kinetic theory of matter. This theory states that matter is made up of particles—atoms and molecules—that are in constant motion. There is a large amount of space (compared to the size of the particle) in between the particles.